/**
   * @fileoverview Rule to restrict what can be thrown as an exception.
   * @author Dieter Oberkofler
   * @copyright 2015 Ian VanSchooten. All rights reserved.
   * @copyright 2015 Dieter Oberkofler. All rights reserved.
   */
  
  "use strict";
  
  //------------------------------------------------------------------------------
  // Helpers
  //------------------------------------------------------------------------------
  
  /**
   * Determine if a node has a possiblity to be an Error object
   * @param  {ASTNode}  node  ASTNode to check
   * @returns {boolean}       True if there is a chance it contains an Error obj
   */
  function couldBeError(node) {
      switch (node.type) {
          case "Identifier":
          case "CallExpression":
          case "NewExpression":
          case "MemberExpression":
          case "TaggedTemplateExpression":
          case "YieldExpression":
              return true; // possibly an error object.
  
          case "AssignmentExpression":
              return couldBeError(node.right);
  
          case "SequenceExpression":
              var exprs = node.expressions;
              return exprs.length !== 0 && couldBeError(exprs[exprs.length - 1]);
  
          case "LogicalExpression":
              return couldBeError(node.left) || couldBeError(node.right);
  
          case "ConditionalExpression":
              return couldBeError(node.consequent) || couldBeError(node.alternate);
  
          default:
              return false;
      }
  }
  
  //------------------------------------------------------------------------------
  // Rule Definition
  //------------------------------------------------------------------------------
  
  module.exports = function(context) {
  
      return {
  
          "ThrowStatement": function(node) {
              if (!couldBeError(node.argument)) {
                  context.report(node, "Expected an object to be thrown.");
              } else if (node.argument.type === "Identifier") {
                  if (node.argument.name === "undefined") {
                      context.report(node, "Do not throw undefined.");
                  }
              }
  
          }
  
      };
  
  };
  
  module.exports.schema = [];